The High Performance Diaphragm liquid end, HPD, combines all of the best characteristics of traditional liquid ends into one technologically advanced design. Its operating characteristics and simplicity of operation make it the best pump to consider first for most metering pump applications. HPD operation is similar to the disc diaphragm in that it is hydraulically actuated and utilizes the same shape and diaphragm. It is similar to a tubular diaphragm in the respect that the process fluid has a “straight through” path through the liquid end. Its low NPSH requirements are similar to that of a packed plunger liquid end. But the primary advantages of the HPD are the unique design features that separate it from traditional designs.
The MARS Advantage
A hydraulically actuated diaphragm liquid end design requires a refill system to compensate for hydraulic fluid that bleeds past the piston or through an air bleed valve during normal operation. Hydraulic fluid is also expelled from the chamber through the internal relief valve when the system experiences excess pressure, and therefore must also be replenished. The HPD features a Mechanically Actuated Refill System (MARS) that offers a number of advantages over traditional refill systems. To understand the advantages of MARS, traditional refill systems must first be explored.
Traditional Designs
Traditional designs use a system that refills the chamber when a vacuum is created by the inability of the diaphragm to move beyond the hydraulic contour plate.